1. Field of the Invention
The present invention generally relates to braking devices for wheelchairs and similar vehicles. More particularly, this invention relates to wheelchair braking device having an uncomplicated construction that can be installed on conventional wheelchairs, and which provides a braking action that automatically disengages when an occupant is seated in the wheelchair.
2. Description of the Prior Art
Wheelchairs are generally equipped with a brake mechanism to enable the user to more safely enter and leave the seat of the wheelchair. Conventional braking mechanisms typically consist of a pair of levers, each engaging the exterior of one of the larger wheels of the wheelchair. To immobilize the wheelchair, the levers must be manually operated to engage the wheels. While such brake mechanisms are reliable, the operator or user of a wheelchair may forget to engage the lever prior to entering or leaving the seat. If the wheelchair is not properly immobilized by the brake, there is a significantly increased risk of the user falling while trying to stabilize him or herself when entering or leaving the wheelchair.
In response, the prior art has suggested various automatic braking systems for wheelchairs. U.S. Pat. Nos. 3,529,700 to Marshall, 4,320,818 to Knoche, 4,623,043 to Babilas, and 5,203,433 to Dugas teach mechanical braking systems that automatically engage when the user rises off the wheelchair seat. Unfortunately, these braking mechanisms are relatively complicated, requiring a complicated mechanical camming system that can be retrofitted to conventional wheelchairs, e.g., Babilas, or requiring considerable modification to the wheelchair itself, e.g., Marshall, Knoche and Dugas. Other braking systems suggested by the prior art have relied on the use of solenoids to engage and disengage a braking lever or pin. For example, U.S. Pat. No. 5,358,266 to Roth et al. discloses a solenoid that operates a bistable braking lever between an engaged and disengaged position, with a large spring acting on the lever to produce the bistable operation. However, the solenoid must be sufficiently powerful to overcome the spring force, such that the solenoid and the battery required to energize the solenoid contribute significantly to the cost of the wheelchair.
From the above, it can be seen that it would be desirable if an automatic braking mechanism were available for wheelchairs, wherein the braking mechanism has a relatively uncomplicated and inexpensive construction, and can be readily mounted to a contentional wheelchair without interfering with the operation of the wheelchair.